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Why can't you use a normal sleeping bag?

This is my first thread here, so please forgive my vast amount of ignorance

I see a lot of threads and great info about top and under quilts. Why doesn't a normal sleeping bag work in a hammock? I understand the air flow under the hammock, but with a full coverage tarp will a normal sleeping bag keep you warm?

I also see the advantage of a top quilt compared to a sleeping bag. I'm thinking it would be much easier to just cover up with a top quilt instead of trying to squirm into a sleeping bag once inside the hammock.

I really appreciate all of the knowledge here, I just wish my search-fu was stronger so I didn't have to be "that guy" asking questions that have been beaten to death already.

You compress the insulation in your sleeping bag when you lay on it, reducing or negating its effect. This is why you should sleep on a pad when ground sleeping---its not a mattress, its insulation that keeps the planet from sucking the warmth out of your body.

Insulation relies on trapping air, which is then warmed by your body. Insulation does not make you warm, it keeps you from getting cold by retaining your body temperature.

Just test the difference. Cheap enough to do. Though I am in total agreement with Sarge.

I am in the process of sewing some grosgrain to a set of sleeping bag compatible zippers. I will then insert shock cord and locks to allow adjustability. Worked great in testing. I figure since the bag is goretex, it has an underquilt protector built in ;-)

Sleeping bags work fine, but typically aren't as light/compressible and TQs. I did try a down TQ and loved it - but I'm too cheap to buy one vs.use the sleeping bags I already have.
I use my sleeping bags along with good bottom insulation (pads or UQ) and wind block (UQP or Pod/sock - I use a warm mummy bag for winter and SnugPak jungle bag for summer. Once you get the hang of it they aren't hard to use in a hammock (it is a skill you need to work on a little to master). I open mine up and lay on top, then zip up as needed. Twist a little to use the hood if required. I have a whole herd of grandkids that use this method as well - not hard to do in Hennessy bottom entry or gathered end hammocks.
If I'm using in warm temps (above about 40F) I use the SB as a TQ by zipping it up to just below my butt, laying right on the hammock, and pulling the SB up over me.
Hope this isn't to confusing.

Last edited by oldpappy; 01-24-2015 at 10:47.

Enjoying the simple things in life.
Hennessey and DIY
2 Seasons: Bug season and too cold for bugs

Some of the answers (so far) to your question are a little misleading. Several people are answering the simple question "Can I use a sleeping bag in a hammock?". The answer is yes. These people are really answering the question "Can a sleeping bag work as a top quilt?". Again, the answer to that is yes. It works fine for that, but you will still need some alternate form of uncompressed insulation under you. I don't feel like the thread has been effectively communicating that to you yet, and that is what you're looking for in your post.

Your questions specifically were:

Originally Posted by Rod Ferro

Why doesn't a normal sleeping bag work in a hammock? I understand the air flow under the hammock, but with a full coverage tarp will a normal sleeping bag keep you warm?

Sarge answered the first question well, but let me be clear, when he says compressing your sleeping bag will reduce or negate its effect that means you CANNOT rely on it to keep the underside of you warm in even mild conditions. If you take the word "reduce" to mean "I can get by with it though it might not be ideal", you'd be dead wrong.

The answer to your second question is a tarp and normal sleeping bag will NOT keep you warm, unless you're just lucky enough to be out in temps which are within a few degrees of where you wouldn't even need the sleeping bag at all. Think of it this way, if you stand still in 45 degree weather in your long underwear in the wind you'll get cold in seconds. Stand the same way with no wind and you'll still get cold in a couple minutes. Lack of obvious wind doesn't mean the warm air that your body generated next to itself doesn't get moved away and replaced by cold air that your body has to heat (again). That tarp would keep you warmer, and slow how quickly you get cold, but you'll still get cold enough to present a danger to you (conditions depending) and it will still tend to happen measured in minutes, maybe not seconds.

A synthetic filled bag can work in very mild conditions. Oddly, the cheaper the better since the cheap stuff doesn';t compress as much and often the outer shell isn't as lightweight either. Of course I would not recommend someone buying a cheap sleeping bag for this purpose, but if someone has an el cheapo laying around, it is ok to try in the backyard. I would not rely on it as ones sole bottom insulation.

Most abhor using a bag in general due to difficulty getting in and squirming around in the hammock. I never had a problem, at least no more of an issue than doing the squirm in a tiny tent. I found that as long as one realizes the butt to sleeping bag contact point is in general a constant, and uses it to ones advantage, the entry into a SB in a hammock isn't so bag. Of course the bottom entry henesseys make it almost impossible. I think since this is where many started their hammock camping, the use of a SB was eliminated very quickly.

"There's a whisper on the night-wind, there's a star agleam to guide us, And the Wild is calling, calling . . . let us go." -from "The Call of the Wild" by Robert Service

DanglingModifier explained it well. I've used a walley world blue pad on the bottom before (closed cell) and it was OK in the summer, but clammy. Not warm enough or wide enough in the winter. The other thing is if you have a single layer hammock, like an ENO, then the pad moves around while you sleep and you'll wake up with a cold backside (CBS in hammock terms). You can get a double layer hammock and put the pad between the layers, which holds the pad in place; however, you will likely still get CBS, unless you add coverage. I've used an inflatable foam pad in the hammock, but you'll have to deflate it a bit to get it to work right (which lessens the insulation value where the most compression is).

A UQ, (especially a full length one) changed hammock camping from good to great. I used sleeping bags as a TQ, but fussing with the zippers and all just wasn't as comfortable as a real TQ.